People stuck in elevators, businesses closed, traffic at a crawl. Life across San Francisco is at a standstill due to a massive power outage affecting tens of thousands of people. Here's a look at some of the best imagery.

Nearly 90,000 customers were affected by this outage. Mayor Lee is now asking PG&E to inspect every substation in the city."See what's old material there, and we need that kind of action from them, and I got the assurance from the new CEO that she will do her best to do it," said Mayor Lee.

An initial investigation suggests a circuit breaker failed, which then caused a fire at the substation on Larkin and Eddy streets. It was in the process of undergoing extensive upgrades. But because water could not be used, it took a long time to reduce the temperature inside the substation. That's why it took so long to restore power.

The mayor believes Friday's event showed how people are likely to react following a significant earthquake.